A spectacular (and spectacularly long) passage from Barth on the church:

To understand this we must above all try to see that over against Jesus Christ the Church is not a chance, i.e., an arbitrary construction. It is not created, formed and introduced by individual men on their own initiative, authority and insight. It is not the outcome of a free undertaking to analyse and come to terms with the self-revealing God by gathering together a community which confesses Him, by setting up a doctrine which expounds and proclaims His truth in the way that seems most appropriate to these men. Applied to such a church, the extra ecclesiam nulla salus would in fact be an enormity. In face of such a church we should all have not only the right but the duty, a duty to faith, to appeal to the free grace of God to be made blessed outside of it. In face of such a church we should have to insist at least upon civil toleration, not only in the name of humanity but in the name of God. A church of that kind has nothing to do with the subjective reality of revelation. We can say quite simply that a church of that description is not the Church but the work of sin, of apostasy in the Church. Naturally none of the fathers whom we mentioned could possibly be thinking of that kind of church. We can and must say, of course, that where the Church is, there also we have always this church which is not the Church, i.e., that in the Church the work of sin and apostasy is always going on as well. There is no time at which to a greater or less degree the Church does not also have the appearance of such a church. There is no time at which to a greater or lesser degree it is not actually a church in this sense. There is no time at which it is quite inappropriate to remember that Jesus Christ is the Lord of the Church, and not the Church the Lord of Jesus Christ. There is no time at which the Church is not compelled by the arbitrary human action which constantly arises at its very heart to remind itself through Holy Scripture of its origin, and to let itself be ruled and therefore corrected from the standpoint of this origin against upstart arbitrarinesses. But the nature of the Church cannot be gathered from man’s upstart arbitrarinesses in it. Just as, similarly, Jesus Christ cannot be understood from the standpoint of man’s nature and kind, which He assumed and adopted, and which are only too familiar to us. What we men apprehend is ultimately and at bottom an accidental or arbitrary search after God, in which we can see only sin against God and a falling away from Him—never the unity between God and man, in which our nature and kind are in Jesus Christ genuinely and finally liberated from such strivings. That there took place in Him revelation and reconciliation between God and man we can comprehend only when we see and understand that the eternal divine Word was here made flesh. It is that which at this point brings light into our darkness. It is that which signifies liberation and purification. It is that which effects revelation and reconciliation. It is that which is the unique reality of the person of Jesus Christ. And the same is true of the Church of Christ. Because it is true of Jesus Christ, it is also true of His Church. The place or area in history at which—and at which alone—reception of revelation is achieved, the visible and invisible coherence of those whom God in Christ calls His own and who confess Him in Christ as their God, in other words the Church, has no reality independent of or apart from Jesus Christ. It is not that because of the sovereignty of their reason, will or feeling men have concluded for Christ or have become “Christians,” i.e., subjects of the predicate Christ. Where that occurs you have sin or falling away. And where any church is only the Christian Church in this sense, namely the church in which Christ is the predicate and not himself the subject, it has itself become the church of sin and apostasy, an heretical church. But the Church of Christ, which really is what it is called, does not exist in this independent reality. Although there is in it no lack of man’s upstart arbitrariness, it exists in dependence on Jesus Christ. And it is because it lives by Jesus Christ, not because it is constantly involved in upstart and arbitrary action, that it is the true Church.

— Karl Barth, CD §16.1 (“The Holy Spirit the Subjective Reality of Revelation”), vol. I.2, pp. 213–14